Here's the police report. And here's an article from the Boston Globe detailing Gates's accusations of racism. Draw your own conclusions [but note that we have a full statement from the cops, and we don't have Gates's side of the story. Here is Gates's version of events. FWIW, even if the cops' story is 100% accurate, I don't see what the point of arresting Gates was. Yelling at a cop isn't a crime, Gates clearly posed no threat to anyone, and the cop should have either used his training to defuse the situation or just walked away--he already knew that Gates wasn't a burglar, which was the original reason for the cops' presence.]

UPDATE: Personally, whenever I encounter cops in a potentially adversarial situation, e.g., during a traffic stop, I become absurdly obsequious, precisely because I know they have the power to arbitrarily arrest me if I piss them off. Law professor or not, the power dynamics in a confrontation with cops is not in your favor.

Joint Press Release from City of Cambridge, Cambridge PD, Middlesex County D.A., and Prof. Gates

The City of Cambridge and the Cambridge Police Department have recommended to the Middlesex County District Attorney that the criminal charge against Professor Gates not proceed. Therefore, in the interests of justice, the Middlesex County District Attorney's Office has agreed to enter a nolle prosequi in this matter.

The City of Cambridge, the Cambridge Police Department, and Professor Gates acknowledge that the incident of July 16, 2009 was regrettable and unfortunate. This incident should not be viewed as one that demeans the character and reputation of Professor Gates or the character of the Cambridge Police Department. All parties agree that this is a just resolution to an unfortunate set of circumstances.